One of the first devices used to amplify signals was the carbon microphone ( effectively a sound-controlled variable resistor ).

By channeling a large electric current through the compressed carbon granules in the microphone, a small sound signal could produce a much larger electric signal.

Telephone hummer / oscillator by A. S. Hibbard in 1890 ( carbon microphone has power gain ); Larsen " used the same principle in the production of alternating current from a direct current source "; accidental development of vacuum tube oscillator ; all at p. 86.

The Boom Operator uses a boom pole, a long pole made of light aluminum or carbon fiber that allows precise positioning of the microphone above or below the Actors, just out of the camera's frame.

In 1877 – 78, Edison invented and developed the carbon microphone used in all telephones along with the Bell receiver until the 1980s.

After protracted patent litigation, in 1892 a federal court ruled that Edison and not Emile Berliner was the inventor of the carbon microphone.

The carbon microphone was also used in radio broadcasting and public address work through the 1920s.

Both Thomas Alva Edison and Emile Berliner filed patent applications for the carbon microphone, in March and June 1877 respectively.

Then, by simply placing a carbon microphone in the transmission line, the strength of the signal could be varied in order to add sounds to the transmission — in other words, amplitude modulation would be used to impress audio on the radio frequency carrier wave.

A " carbon amplifier " consisting of a carbon microphone and an electromagnetic earpiece sharing a common membrane and case.

* Telephone ( carbon diaphragm microphone ), filed August 1879, issued December 1879

These microphones evolved from the carbon microphones used in the early days of aviation and the telephone which relied on a DC bias voltage across the carbon microphone element.

For example, in developing the carbon microphone ( or carbon grain transmitter ) that became the basis of telephones of the next hundred years, Edison and his co-workers tried hundreds of substances, finally settling on lamp black as the variable resistance medium.

* October 1876: Thomas Edison tests his first carbon microphone.

* 4 June 1877: Emile Berliner files telephone patent application that includes a carbon microphone transmitter.

* 1 December 1877: Western Union enters the telephone business using Thomas Edison's superior carbon microphone transmitter.

* 3 May 1892: Thomas Edison awarded patents for the carbon microphone based on applications lodged in 1877.

Their first experiment used a carbon microphone.

" Can you hear me ?," Earle C. Anthony would yell into a carbon microphone from his garage transmitter location.

In 1862, Reis demonstrated his telephone to Wilhelm von Legat, Inspector of the Royal Prussian Telegraph Corps who produced an account of it ( Legat, 1862 ), a translation of which was obtained by Thomas Edison in 1875 and was used in Edison's successful development of the carbon microphone.

The first electrical complete recording ( using a single carbon microphone ) was made in 1928, by Harrison, Elgar and the London Symphony Orchestra.

The anode plug ( Figure 2 ) was inserted into a carbon anode holder.

To reduce heat transfer from the hot gas to this anode holder outside the regime of the arc, a carbon shield was attached to the surface providing an air gap of 1/16 inch between the plate and the surface of the anode holder.

In addition, the inner surface of the carbon shield was covered with aluminum foil to reduce radiation.

The mixture was then extracted with alkali and with water following which the carbon tetrachloride was distilled on a Vigreux column, a 25% center cut being retained which was then degassed under vacuum in the presence of Af.

The required amount of carbon tetrachloride was distilled into a series of reaction cells on a manifold on a vacuum line.

The light was filtered by the soft glass window of the thermostat thus ensuring that only light absorbed by the chlorine and not by the carbon tetrachloride could enter the reaction cell.

In the liquid phase runs the amount of carbon tetrachloride in each reaction tube was determined by weighing the tube before opening and weighing the fragments after emptying.

The fraction of exchange was determined as the ratio of the counts / minute observed in the carbon tetrachloride to the counts / minute calculated for the carbon tetrachloride fractions for equilibrium distribution of the activity between the chlorine and carbon tetrachloride, empirically determined correction being made for the difference in counting efficiency of Af in Af and Af.

Calcium hydride was substituted for Af as a drying agent for carbon tetrachloride.

The liquid phase photochemical exchange between chlorine and carbon tetrachloride was more reproducible than the thermal exchange, although still erratic.

-- Although there was some variation in results which must be attributed either to trace impurities or to variation in wall effects, the photochemical exchange in the gas phase was sufficiently reproducible so that it seemed meaningful to compare the reaction rates in different series of reaction tubes for the purpose of obtaining information on the effect of chlorine concentration and of carbon tetrachloride concentration on the reaction rate.

Argon ( αργος, Greek meaning " inactive ", in reference to its chemical inactivity ) was suspected to be present in air by Henry Cavendish in 1785 but was not isolated until 1894 by Lord Rayleigh and Sir William Ramsay in Scotland in an experiment in which they removed all of the oxygen, carbon dioxide, water and nitrogen from a sample of clean air.

Pig iron, a very hard but brittle alloy of iron and carbon, was being produced in China as early as 1200 BC, but did not arrive in Europe until the Middle Ages.

However, very small amounts of steel, ( an alloy of iron and around 1 % carbon ), was always a byproduct of the bloomery process.

This method introduced carbon by heating wrought iron in charcoal for long periods of time, but the penetration of carbon was not very deep, so the alloy was not homogeneous.

Puddling was introduced during the 1700s, where molten pig iron was stirred while exposed to the air, to remove the carbon by oxidation.

The uses of carbon and its compounds are extremely varied.

Worker at carbon black plant in Sunray, Texas ( photo by John Vachon, 1942 ) Pure carbon has extremely low toxicity to humans and can be handled and even ingested safely in the form of graphite or charcoal.

In turn, zinc hydroxide reacts with carbon dioxide in the atmosphere to yield a thin, impermeable, tenacious and quite insoluble dull gray layer of zinc carbonate which adheres extremely well to the underlying zinc, so protecting it from further corrosion.

Alloys with less carbon than this, such as wrought iron, cannot be heat treated to a significant degree and will consequently be of low hardness, while a higher carbon content creates an extremely hard but brittle material that cannot be annealed, tempered, or otherwise softened.

The solid core NTR fuel itself is conventionally a small percentage of U-235 buried well inside an extremely strong carbon or carbide mixture.

Stable isotope ratios have been used in botanical and plant biological investigations for many years, and more and more ecological and biological studies are finding stable isotopes ( mostly carbon, nitrogen and oxygen ) to be extremely useful.

Without proper ventilation, carbon monoxide can be extremely dangerous and can vary from a small, limited amount to a lethal amount.

When the hotter sections of the discs reach extremely high temperatures ( 1200 – 1300 degrees Fahrenheit ), the carbon within the cast iron of the disc will react with the iron molecules to form a carbide known as cementite.

A searchlight ( or spotlight ) is an apparatus that combines an extremely luminous source ( traditionally a carbon arc lamp ) with a mirrored parabolic reflector to project a powerful beam of light of approximately parallel rays in a particular direction, usually constructed so that it can be swiveled about.

; Class N: Class N planets have a reducing environment and are barren and rocky with extremely high surface temperatures caused by thick atmospheres containing carbon dioxide and corrosive sulfides.

When combined with a plastic resin and wound or molded it forms carbon fiber reinforced plastic ( often referred to as carbon fiber ) which has a very high strength-to-weight ratio, and is extremely rigid although somewhat brittle.

Unfortunately, projection required an extremely bright and therefore hot light source ( a carbon arc or a 500 watt bulb were typical ) and could visibly " fry " the plate if continued for more than two or three minutes, causing serious damage to the color.

The probe itself would consist of a mesh of extremely fine carbon wires about 100 m across, with the wires spaced the same distance apart as the 3-mm wavelength of the microwaves that will be used to push it.

* Carbon print: This is an extremely delicate print made by coating tissue paper with potassium bichromate, carbon black or another pigment and gelatin.

The two pieces of tape to be joined were painted with a solution of extremely fine iron filings suspended in carbon tetrachloride, a toxic and carcinogenic compound.

When it was used, the two pieces of tape to be joined were painted with a solution of extremely fine iron filings suspended in carbon tetrachloride, a toxic and carcinogenic compound.

Signs of unrest will almost certainly precede any future eruptive activity from Mount Pelée, and its past activity ( including the violent eruptions uncovered by carbon dating ) is an extremely important factor for hazard assessment.

While the interstitial carbon diffuses readily even at moderate temperatures the self-diffusion of iron becomes extremely slow at temperatures below 600 ° C until, for all practical purposes, it stops.

Some smoke alarms use a carbon dioxide sensor or carbon monoxide sensor to detect extremely dangerous products of combustion .< ref name = senseair > However, gas sensors able to warn of poisonous levels of those gases in the absence of a fire have sensitivities based on the uptake of carbon monoxide by haemoglobin, and are not generally sensitive or fast enough to be used as fire detectors.